Carputer pics part 4: Building the computer
When building a computer for use in a car, there's a few things to consider... power, heat, size, shock protection.
Getting the easy stuff out of the way, I started with a small form factor (SFF) box. It's a P2 so it's not so power hungry and doesn't run as hot as today's current systems.
Next I swapped out the standard HD for a laptop drive. Being designed for laptops, they're much more shock tolerant than desktop HDs. When I mount the computer in the car, I'll also add some shock protection there... not sure exactly what form yet.
The first hard part was the power supply. Having previously speced one out and ordered it, it was time to install it. Putting the new PS where the old one was would put it too far for the ATX connector to reach the mobo :( Instead, I had to put it where the HD was. Of course, I then had to relocate the HD. After a quick trip to Home Depot for some self-tapping screws, my cousin Eric helped me get it all mounted:
The PS is mounted with standard mobo standoffs and is pretty securely in place.
With a computer that is now wired for 12v DC, I needed some sort of power plug. The PS came with wires, but I didn't want to just solder it into the car... makes upgrades tough :) So I took a 18" power cord that's used as a pass-through (from older PCs to their monitors so you have one switch that turns everything off). I cut it in half and soldered half into the carputer's PS. I soldered the other half into the car. Now I can easily plug and unplug the carputer.
The next hurdle was that taking the carputer out to the car for testing, I ran into a problem. It booted up ok, but didn't login to my wifi AP. Without a monitor and keyboard, I had no way of knowing what was wrong (software error, low power, weak signal...). So now I needed a way to power the carputer in the house for debugging.
Getting 12v DC shouldn't be hard... just use an old PC power supply. Well, it's not quite that easy :( An ATX power supply won't turn on until the mobo tells it to. So when it's not in a computer, how do you tell it to turn on? I found a couple guides on the 'net, but they didn't match up to what I was seeing with my volt meter. Turns out, I had an old Dell PS from a time when Dell made PSs with an ATX connector, but all the pins in different places.
Tossing the Dell PS, I got a real one and figured out which pins to short. Still no go :( More reading... turns out that you also have to put a load on the PS or it won't turn on. So I hooked up an HD from another machine:
that's the carputer under my testing PS and it's powering the HD in the case just so the PS will turn on. A bit odd, but it worked great.
Also note that for the carputer's PS to turn on, it waits for 5 seconds after the car starts (which is why it doesn't count as a load on the ATX power supply at first).
I also needed a way to simulate the ignition switch from the car on my new power supply. Scavenging the power button from a dead PC, I mounted it inside the PS with just the button sticking out:
Using another power cord, I put a plug on the PS so that I could power the carputer. Time to be very careful.... this standard looking plug has 3 pins, but they're: +12, Gnd, Ignition.... not 110AC!
I carefuly chose to put the proper end on the carputer side so that while it's in the house, it can't be plugged into an outlet with a normal cord:
Hacking a bit with a dremel, I added an on/off switch and mounted an old, dead HD to the top:
With this rather atypical setup, I'm now able to use the carputer in the house for testing/debugging/upgrading. A few quick fixes and now it's ready to go in the car.
Getting the easy stuff out of the way, I started with a small form factor (SFF) box. It's a P2 so it's not so power hungry and doesn't run as hot as today's current systems.
Next I swapped out the standard HD for a laptop drive. Being designed for laptops, they're much more shock tolerant than desktop HDs. When I mount the computer in the car, I'll also add some shock protection there... not sure exactly what form yet.
The first hard part was the power supply. Having previously speced one out and ordered it, it was time to install it. Putting the new PS where the old one was would put it too far for the ATX connector to reach the mobo :( Instead, I had to put it where the HD was. Of course, I then had to relocate the HD. After a quick trip to Home Depot for some self-tapping screws, my cousin Eric helped me get it all mounted:
The PS is mounted with standard mobo standoffs and is pretty securely in place.
With a computer that is now wired for 12v DC, I needed some sort of power plug. The PS came with wires, but I didn't want to just solder it into the car... makes upgrades tough :) So I took a 18" power cord that's used as a pass-through (from older PCs to their monitors so you have one switch that turns everything off). I cut it in half and soldered half into the carputer's PS. I soldered the other half into the car. Now I can easily plug and unplug the carputer.
The next hurdle was that taking the carputer out to the car for testing, I ran into a problem. It booted up ok, but didn't login to my wifi AP. Without a monitor and keyboard, I had no way of knowing what was wrong (software error, low power, weak signal...). So now I needed a way to power the carputer in the house for debugging.
Getting 12v DC shouldn't be hard... just use an old PC power supply. Well, it's not quite that easy :( An ATX power supply won't turn on until the mobo tells it to. So when it's not in a computer, how do you tell it to turn on? I found a couple guides on the 'net, but they didn't match up to what I was seeing with my volt meter. Turns out, I had an old Dell PS from a time when Dell made PSs with an ATX connector, but all the pins in different places.
Tossing the Dell PS, I got a real one and figured out which pins to short. Still no go :( More reading... turns out that you also have to put a load on the PS or it won't turn on. So I hooked up an HD from another machine:
that's the carputer under my testing PS and it's powering the HD in the case just so the PS will turn on. A bit odd, but it worked great.
Also note that for the carputer's PS to turn on, it waits for 5 seconds after the car starts (which is why it doesn't count as a load on the ATX power supply at first).
I also needed a way to simulate the ignition switch from the car on my new power supply. Scavenging the power button from a dead PC, I mounted it inside the PS with just the button sticking out:
Using another power cord, I put a plug on the PS so that I could power the carputer. Time to be very careful.... this standard looking plug has 3 pins, but they're: +12, Gnd, Ignition.... not 110AC!
I carefuly chose to put the proper end on the carputer side so that while it's in the house, it can't be plugged into an outlet with a normal cord:
Hacking a bit with a dremel, I added an on/off switch and mounted an old, dead HD to the top:
With this rather atypical setup, I'm now able to use the carputer in the house for testing/debugging/upgrading. A few quick fixes and now it's ready to go in the car.
posted by The Amigo at 9:02 PM
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2 Comments:
I'm guessing you've already considered this option but I figured it wouldn't hurt to point to it anyway. :)
--Lisa
That would be a nice option to add. Maybe some day in the future. We have a few of those cards in my dept here at work.
With an Ev-DO card you can get >1Mbps if you've a good signal. The coverage is almost as complete as cell phones get (compared to WiFi where I don't expect to get more than a couple seconds from any given AP as I drive by).
The main reason I'm going with WiFi (for now) instead of EvDO is because Verizon charges $80/mo for unlimited usage. WiFi is free :)
Sprint should be rolling out EvDO soon so we may see some competition, but I don't know how it will effect prices. My department does traing for CDMA carries (which includes Sprint and Verizon) and also includes EvDO. The EvDO classes are one of our new offerings. If I were to sit in one of them, I might actually learn how it works... for now, I just know it's wireless internet access with pretty good coverage and throughput. :)
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